Computer programming or coding is the composition of sequences of instructions, called programs, that computers can follow to perform tasks. It involves designing and implementing algorithms, step-by-step specifications of procedures, by writing code in one or more programming languages. Programmers typically use high-level programming languages.

Code review (sometimes referred to as peer review) is a software quality assurance activity in which one or more people examine the source code of a computer program, either after implementation or during the development process. The persons performing the checking, excluding the author, are called "reviewers". At least one reviewer must not be the code's author.

In computer programming and software design, code refactoring is the process of restructuring existing source code—changing the factoring—without changing its external behavior. Refactoring is intended to improve the design, structure, or implementation of the software (its non-functional attributes), while preserving its functionality.

In computer science, program optimization, code optimization, or software optimization is the process of modifying a software system to make some aspect of it work more efficiently or use fewer resources. In general, a computer program may be optimized so that it executes more rapidly, or to make it capable of operating with less memory storage or other resources, or draw less power.

System testing often serves the purpose of evaluating the system's compliance with its specified requirements - often from a functional requirement specification, a system requirement specification. System testing can detect defects in the system as a whole. System testing can verify the design, the behavior and even the believed expectations of the customer.

Bug fixing is the process of identifying, reproducing, and patching errors or flaws in software. It follows a systematic workflow: isolating the root cause, applying a code change, and verifying the fix to ensure it doesn't introduce new issues.